The present invention relates generally to weight training exercise machines having a vertical stack of weights and, more particularly, pertains to an apparatus and method for adjusting resistance to an exercise motion incrementally in a balanced manner.
So-called selectorized weight machines have been used in fitness clubs, gyms and athletic training facilities for many years. These machines allow the user to select the amount of weights on a weight stack which will be lifted during the exercise and training protocol. A particular version of a selectorized weight machine is one which allows for variable resistance along the range of motion of the exerciser training protocol. These selectorized, variable-resistance weight machines utilize an operating mechanism such as a cam having a varying radius or profile. Cable means of some kind, such as a wire cable, a chain, a belt, or the like is attached at one end of the cam, and is attached at the other end to the top of a selector bar passed through and connected to a weight stack. When the user rotates a force transmission means fixed to the cam, the cam rotates and winds up the cable, chain, etc., thereby lifting the weights from the weight stack along guide rods. The changing cam profile varies the mechanical advantage of the weights which the user encounters. The cam profile is designed to approximate the change in anatomical mechanical advantage of the user at each point in the range of motion.
Although exercise weight stacks are prevalent in the exercise industry, they nonetheless are subject to certain shortcomings. For example, in order to provide a sufficiently large amount of weight at a reasonable cost, equipment manufacturers generally use weight plates of relatively large mass. As a result, the weight being lifted cannot be adjusted in small increments.
Attempts have been made to remedy the need for incremental adjustment. For example, one known design depends upon a small weight stack connected to the end of the main weight stack. Another uses a system that allows the user to slide small weights onto a pin projecting from the front of the stack. However, both of these devices are deficient in maintaining the balance of the weight stack during use.
It is extremely important that the weight stack is raised by the cable or belt at the center of the top plate in the weight stack. If it is not, the plates will hang down on the heavy unbalanced end causing them to bind on the guide rods making operation of the machine rough. A related problem caused by an unbalanced weight stack is that over a period of time, the bushings in the top plate risers will wear, allowing the top plate to tip. If it tips enough, the selector bar in the center of the stack drags in the center holes of the plates that are not being lifted. It is likely with enough wear that the selector bar will miss the center holes in the plates not being lifted. With the lifted part of the stack not being balanced, a selector bar will strike the upper surface of the top plate or the top portion of the stack portion not being lifted causing the lifting portion of the stack to become jammed in a partially raised position. It has happened in the past, that not cognizant of the consequences, the exerciser on the machine would push the selector bar such that it would re-enter the center holes of the non-lifted portion of the stack, allowing the lifted portion of the stack to drop down on the exerciser""s hand causing severe injury.
One weight stack exercise machine concerned with overcoming these problems is disclosed in co-pending U.S. patent application Ser. No. 09/527,000 filed Mar. 16, 2000 which is commonly assigned to the assignee of this application. In this disclosure, a weight stack adjusting system is provided for an exercise machine having a frame, an operating mechanism movably connected to the frame, a resisting structure on the frame and a connecting device entrained about a first pulley and a second pulley. Both pulleys are mounted on the frame and join the operating mechanism with the resisting structure so as to selectively allow moving the resisting structure between a raised position and a lowered position. The system includes a first guide rod, a second guide rod, a third guide rod, and a fourth guide rod, each being supported by the frame. The resisting structure is formed by a primary weight stack movably mounted on the first and second guide rods, and a supplementary weight stack movably mounted on the third and fourth guide rods. A main drive belt has a first end connected to the operating mechanism, an intermediate portion entrained about the first pulley so as to define a first vertical path tangent to the first pulley, and a second end joined to a center of the top plate of the primary weight stack. An auxiliary drive belt has a first end connected to the main drive belt at a junction forwardly of the first vertical path defined by the main drive belt, an intermediate portion wrapped around the second pulley so as to define a second vertical path tangent to the second pulley, and a second end secured to a center of a top plate of a supplementary weight stack. Although this exercise machine has performed generally satisfactorily, there have been a few problems experienced in the movement of the auxiliary drive belt. Additionally, not all exercise machines are designed to adapt the third pulley and the connected drive belt arrangements in their frames.
Not withstanding this prior art, it remains desirable to provide an improved weight stack exercise machine which enables the user to easily adjust the increment with which the weight or resistance can be increased or decreased. Likewise, it is also desirable to provide a multi-stack exercise machine in which each weight stack remains balanced so that jamming is prevented during the exercise motion. Additionally, it would be desirable to improve upon the weight exercise machine disclosed in the aforementioned co-pending patent application by eliminating the auxiliary drive belt and third pulley.
The invention advantageously provides dual weight stack exercise equipment which overcomes the disadvantages or drawbacks of the prior art. The weight stacks may be utilized with a variety of exercise apparatus to permit a user to vary weight employed by substantially any desired small increment. The invention has utility for those interested in maintaining health and fitness, as well as for those involved in physical therapy and rehabilitation from injury.
It is one object of the present invention to provide an exercise machine having structure for incrementally adjusting resistance to an exercise motion.
It is another object of the present invention to provide a balanced weight stack in an exercise machine which avoids jamming.
It is also an object of the present invention to provide a dual weight stack arrangement in an exercise machine which creates various levels of resistance.
It is a further object of the present invention to provide an exercise machine which minimizes injury to a user during use thereof.
It is an additional object of the present invention to provide a method of adjusting weight resistance in an exercise machine using a combination of side-by-side weight stacks.
Yet another object of the present invention is to provide a multi-stack exercise machine having a primary weight stack with one size of weights and a supplementary weight stack having a second and different size of weights.
A still further object of the present invention is to provide a variable resistance exercise machine which is simple in structure and easy to operate.
The invention contemplates a weight stack adjusting system for an exercise machine having a frame, an operating mechanism movably connected to the frame, resisting structure on the frame and a connecting device entrained about a first pulley and a second pulley, both being mounted on the frame and joining the operating mechanism with the resisting structure so as to selectively move the resisting structure between a raised position and a lowered position. The system includes a first guide rod, a second guide rod, a third guide rod and a fourth guide rod, each being supported by the frame. The resisting structure is formed by a primary weight stack having a plurality of plates including a top plate movably mounted on the first and second guide rods, and a supplementary weight stack having a plurality of plates including a top plate movably mounted on the third and fourth guide rods. The invention is improved wherein a coupling arrangement is disposed upon the primary weight stack top plate and the supplementary weight stack top plate, and interconnects the primary weight stack and the supplementary weight stack together such that a lifting force applied through the connecting device will simultaneously lift the primary weight stack and the supplementary weight stack in a balanced manner.
The coupling arrangement includes a force distribution assembly attached to the primary weight stack top plate and a carriage structure movably mounted on the second guide rod and the supplementary weight stack top plate. The force distribution assembly is connected between the first guide rod and the second guide rod and is disposed along the longitudinal centerline of the primary weight stack top plate. A drive belt has a first end connected to the operating mechanism, an intermediate portion entrained about the second pulley so as to define a first vertical path tangent to the second pulley, and a second end joined to a center of the top plate of the primary weight stack. The second end of the drive belt is joined to the center of the top plate of the primary weight stack by a cable clamp. The carriage structure includes a pair of spaced apart carriage plates, each of the carriage plates having a distal end supported on the cable clamp, and a proximal end pivotally connected to the top plate of the supplementary weight stack. A pair of rollers is rotatably mounted between the carriage plates, each of the rollers being slidably mounted for rolling movement along opposite sides of the second guide rod. The proximal ends of the carriage plates are interconnected by a horizontal member having a downwardly depending tab overlying an upwardly extending tab projecting from a collar located in the center of the top plate of the supplementary weight stack. The downwardly depending tab and the upwardly extending tab are pivotally joined together by a chain link. A first selector pin is engagable with plates of the primary weight stack, and a second selector pin is engagable with plates of the secondary weight stack. The force distribution assembly and the carriage structure include cylindrical tubes for retaining the first selector pin and the second selector pin. The supplementary weight stack is preferably located behind the primary weight stack.
The invention also contemplates a method of adjusting weight resistance in an exercise apparatus having a movable operating mechanism connected to a resisting structure by a connecting device entrained about a first pulley and a second pulley, each of which has an axis of rotation. The method includes the steps of providing a frame having a first guide rod, a second guide rod, a third guide rod and a fourth guide rod; and providing the resisting structure in the form of a stack of primary weights movably mounted on the first and second guide rods and a stack of supplementary weights movably mounted on the third and fourth guide rods. The invention is improved by providing a coupling arrangement which is disposed upon the primary weight stack top plate and the supplementary weight stack top plate and interconnects the primary weight stack and the supplementary weight stack together such that a lifting force supplied through the connecting means will simultaneously lift the primary weight stack and the supplementary weight stack in a balanced manner. The method includes the step of providing the connecting device in the form of a drive belt having a first end connected to the operating mechanism, an intermediate portion entrained about the second pulley so as to define a first vertical path tangent to the second pulley, and a second end joined to a center of a top plate of a primary weight stack. The method further includes the step of locating the supplementary weight stack behind the primary weight stack. The method also includes the step of providing a first selector arrangement for the primary weight stack and a second selector arrangement for the supplementary weight stack whereby a user of the exercise machine uses at least one of the selector arrangements to define the resisting structure for the operating mechanism.